The present invention relates to an apparatus and method for forming lubricant recesses having minute configurations on a curved inner surface, and more particularly, to an apparatus and method for forming lubricant recesses having minute configurations by applying a photolithograph method in a curved inner surface, such as a cylinder bore surface of a cylinder block, the inside of a cylinder liner, the inside of a compressor cylinder, a big end of a connecting rod, a big end bearing, a shaft insertion hole of a rocker arm, or the like in an internal combustion engine.
Various compressors and internal combustion engines may be machines that operate by combining the reciprocating motion of a piston in a cylinder liner or cylinder bore with the rotation motion of a crankshaft through a connecting rod connected to the piston. In such a compressor or internal combustion engine, considerable friction and abrasion may occur between a piston ring and a cylinder bore surface or a cylinder liner, between a connecting rod and a crankshaft, or between a shaft insertion hole of a rocker arm and a rocker arm shaft disposed inside the shaft insertion hole. Thus, various technologies for reducing the friction and abrasion are being developed.
Furthermore, to reduce the friction, various technologies for surface-treating or modifying surfaces of a cylinder bore or cylinder liner, a piston ring, a piston skirt, a big end of a connecting rod, and a big end bearing are being developed. For example, a technology in which lubricant recesses containing a lubricant therein is installed in a frictional surface to form an oil film on the frictional surface, thereby improving lubrication performance and reducing friction and abrasion, and thus improving durability is attempting.
There are various methods for forming lubricant recesses in a frictional surface. For example, a method in which a frictional surface is cut by using a super hard tool or thermally treated processing tool to form lubricant recesses is disclosed in Korean Utility Model Registration No. 20-0409695. Also, a method in which laser is directly irradiated onto a cylinder bore surface to form lubricant recesses is disclosed in Japanese Patent Publication Nos. 2006-255813 or 2008-144937.
Among these methods, the mechanical processing method or the method using the laser may have a limitation in common in that a processing time increases in proportion to the number of lubricant recesses. In an actual application, in case of an engine block, lubricant recesses may be limitedly formed on the vicinity of a top dead point of a piston. In case of a method using a photolithograph process, lubricant recesses to be formed within a cylinder bore may be formed at a time regardless of the number of lubricant recesses or an area of the respective lubricant recesses. However, a technology in which a cylinder block having a plurality of cylinder bores is processed at a time is as yet undeveloped.